@Jarett Welcome to the forum
Like @toolboy said Any program you get for HVAC duct is also going to need to be run through the post processor of firecontrol before being used.
I ve laid out fittings mostly by hand in Fusion and use a few random programs for pipe branch’s. If you find any inexpensive or free HVAC program please let me know.
Here is a link to a few fittings i’ve posted
I recently upgraded to a XR so I could build more fittings with and table, the pro was a little small for HVAC.